13 replies to this topic

[JamesC]

I was under the impression that the turbo in my VXT contains a recirculating waste gate, however I appear to get a 'macdonalds car park' style hiss on lifting off the throttle. I dont recall this on my previous VXT so I can only assume a previous owner has fitted an aftermarket one. The trouble is I have been trying to look for it and it certainly isnt jumping out at me. Where would it be fitted if it were there? Or would the stage 1 remap increase the boost pressure thus making the noise more noticeable in the OEM valve? Apologies for the noob questions here!

[Zoobeef]

They may of removed the baffles or fitted an aftermarket air filter and therefore you'll be able to hear it more. It they had fitted one though it'll be between the top hat and the intercooler. Is it a hiss or a chatter?

[siztenboots]

it has two systems ,

1) a solenoid mounted on the turbo that controls boost pressure to the actuator, this opens/closes the wastegate.



2) a solenoid on the inlet manifold that controls stored vacuum fed to open the recirc valve on the turbo compressor, which allows excess output boost to be fed back to the input side of the compressor through an internal pathway. In the pic above, its rubber hose is just shown turned 180 and tucked away, its normally fed by a larger bore hard plastic hose.

[JamesC]

It is more of a hiss. I hadnt considered the air filter, the previous owner told me the air box had been 'drilled' I guess to make induction noise louder, could this be the cause?

[SteveA]

It is more of a hiss. I hadnt considered the air filter, the previous owner told me the air box had been 'drilled' I guess to make induction noise louder, could this be the cause?

Bang on, that is exactly what it is.

[JamesC]

It is more of a hiss. I hadnt considered the air filter, the previous owner told me the air box had been 'drilled' I guess to make induction noise louder, could this be the cause?

Bang on, that is exactly what it is.

Thanks, when I finally get on with my suspension refresh will have to get at the air box and see if I can replace/repair it.

[SteveA]

Why? Most of the main tuners do this as part of their upgrades.

[Rickwoo118]

It is more of a hiss. I hadnt considered the air filter, the previous owner told me the air box had been 'drilled' I guess to make induction noise louder, could this be the cause?

Definately the air filter. I quite like mine hissing.

Edited by Rickwoo118, 30 August 2012 - 10:17 AM.

[JamesC]

Is it more efficient 'drilled' than fed as per the OEM intent?

[P11 COV]

Is it more efficient 'drilled' than fed as per the OEM intent?

Yes. It reminds me of when I put a ITG filter on mine. I felt like a right Chav. :-)

[Apex Graphics]

I drilled my air box as part of the mods I did, better for airflow and sounds good, why on earth go backwards & replace it?!

[JamesC]

Don't get me wrong I like the induction sound but wasn't sure it is having a positive effect. If the consensus is that that it's beneficial then I will leave it.

[hairy]

excellent photo STB

[siztenboots]

that photo is from a GSI, the heat shield is different, tempted to mod it for the VX , the hole on the left is where the crankshaft sensor should be, the toothed trigger wheel is just visible.